Concreting FAQs, Toowoomba

A handful of things, and none of them can be judged from your kitchen table. The first is the area in square metres, since a bigger pour uses more material and more labour. The second is the finish: plain concrete is the simplest, while exposed aggregate, coloured and polished finishes add process and cost more. The third is what is already there, because breaking out an old slab, carting the rubble away and excavating a proper base all take time before a single wheelbarrow of new concrete arrives. The fourth is access, which on a steep or tight block can swing a job's price a long way, and the last is the ground itself, which on the Downs usually means deep reactive black soil that needs engineered footings. That is why every job needs a site visit. Ring us with your suburb and roughly what you want done and we will get a local concreter to come and price it properly rather than throw you a number that changes the moment they turn up.

Both are common around Toowoomba and both matter. Plenty of blocks on the eastern escarpment around Prince Henry Heights, Redwood, Rangeville and Mount Lofty are steep, which changes how the concrete gets from the truck to the formwork. If a truck can back up and chute straight in, that is the quickest and cheapest way. If it cannot, the mix has to be pumped or barrowed, which means more people and more hours, and a steep site can also need extra formwork, steps or a stepped pour. The black-soil plains out to the west at Westbrook and Glenvale are a different problem: the deep reactive clay moves as it wets and dries, so the base has to be prepared and the footings designed for it rather than poured as an afterthought. A concreter who works your area already knows which of these applies before they arrive.

It is the single biggest local concreting issue, and it is worth understanding before you pour. Much of the Darling Downs sits on deep reactive black cracking clay that swells when it takes up moisture and shrinks back when it dries, and it moves more than almost any soil in Australia. A slab or driveway laid straight onto it without allowing for that movement will crack, lift and heave as the seasons turn. The answer is engineering rather than luck: deep footings or a stiffened or waffle raft, articulation joints in the right places, and the correct steel through the slab so the ground can move without tearing the concrete apart. It is not expensive to build in at the start and it is the difference between a slab that lasts and one that fails. A concreter who works the Downs allows for the soil as a matter of course.

It does, and Toowoomba feels it more than most of Queensland because the city sits up around 700 metres on the Great Dividing Range. Winters bring hard frosts and the occasional light snow, and you do not pour concrete into a frost, because water freezing in a fresh mix wrecks the surface and the strength. The reaction that hardens concrete also runs slower in the cold, so a winter pour takes longer to cure and cars stay off it for longer. A good crew works around it by timing the pour for the warmer part of the day, protecting a fresh slab overnight, and not rushing the cure. Summers are hot too, which brings the opposite problem of concrete going off too fast, so the season shapes how any job is planned.

Sealing is not compulsory but it earns its keep, particularly on decorative and exposed aggregate finishes. A sealer slows staining from oil, leaves and general traffic, keeps colour from fading as fast, and adds a layer of protection to the surface. It is not permanent. It wears off over time and needs redoing periodically, and how often depends on the product used and how much sun and traffic the area cops. Ask your concreter what they have put down, because the product determines the reseal interval, and there is no single answer that fits every job.

The slab sitting on your own land generally does not need approval, but the part where your driveway crosses the footpath and nature strip to meet the road, the vehicular crossing, does need approval from Toowoomba Regional Council, and the Council has its own specifications for how it is built. That covers the width, the profile, the materials and how it ties into the kerb. Stormwater and drainage can also come into it on some blocks, because the region has seen serious flash flooding and the water off a new hard surface has to go somewhere sensible rather than into a neighbour's yard. A concreter who works the region will usually know the local requirements and how to arrange the crossing, but the approval itself sits with the Council, so it is worth raising early rather than after the pour.

Walking is usually fine within a day or so, once the surface has hardened enough not to mark. Driving is a different matter. You should generally keep cars off a new driveway for about a week, and heavier vehicles such as trucks, caravans or a loaded trailer for longer again. Concrete keeps gaining strength for weeks after it looks finished, so the surface being hard underfoot does not mean it is ready to carry a car. Your concreter will give you a specific time based on the mix, the thickness and the weather on the day. In the cooler months the reaction that hardens concrete runs slower, and Toowoomba's cold winters and hard frosts up on the Range make that more pronounced, so a winter pour here will sit at the longer end.

Winter is fine, it just moves more slowly, and a good crew avoids pouring into a frost because freezing damages a fresh surface. Cold slows the chemical reaction that hardens concrete, so curing takes longer and the concreter may adjust the mix or the finishing schedule to suit. Rain is the bigger problem, and the Downs gets its share of it. Water landing on a fresh surface before it has set can weaken and mark the finish, so pours get postponed when the forecast is poor. It is frustrating to have a job pushed back a few days, but a concreter who reschedules you because of rain is doing right by your slab. Trying to pour through a downpour to keep to a date is how you end up with a surface that never looks right.

All concrete cracks to some degree. It shrinks as it cures and it moves with temperature and ground conditions, and it has very little ability to stretch. Around Toowoomba the reactive black soil makes this a bigger issue than most places, because the clay swells and shrinks under the slab through the seasons, so the footings and steel have to be designed to cope with that movement. The job of a good concreter is not to stop cracking outright, which cannot be done, but to control where it happens using control joints, articulation, correct steel and a properly compacted base. Fine hairline cracks are normal and cosmetic and are nothing to lose sleep over. What is worth a look is a wide crack, a crack with a step or height difference across it, or a crack that keeps growing, because those usually point to the ground moving underneath, poor base prep, or drainage that has failed. If you are seeing that, get someone to look at it rather than filling it and hoping.

It depends entirely on what is going on top of it. A residential driveway carrying cars is typically around 100mm with reinforcing mesh through it. Anything carrying heavier loads, a truck, a caravan, a boat trailer or an industrial hardstand, needs more thickness and heavier reinforcement. Ground conditions change it too, and this matters a lot on the Downs. The deep reactive black soil across Toowoomba can call for a thicker, stiffened slab with heavier steel and engineered footings so the ground movement does not crack it. Your concreter should specify the thickness and steel for your particular job rather than pouring a default, and it is a perfectly fair question to ask when they quote you.

Often, yes. If the existing slab is structurally sound, not badly cracked and has not dropped or moved, resurfacing is usually cheaper and faster than demolition and a fresh pour, and it saves you the mess of breaking the old one out. If the slab has deep cracks, a step across a crack, or drainage that has failed, an overlay just puts a new surface over the same problem and it will come back through within a season or two. Someone needs to stand on it and look at it to tell you honestly which situation you are in. It is one of those calls that cannot be made from a photo.

The whole region. That covers the established suburbs like Rangeville, Middle Ridge, Centenary Heights, Kearneys Spring, Newtown, Harristown, Wilsonton and Mount Lofty, the Range-edge blocks at Prince Henry Heights and Redwood, and the growth areas out west and north at Glenvale, Cotswold Hills, Westbrook, Darling Heights, Drayton, Highfields and Kleinton. Our suburbs page lists everywhere we work in detail.